Acoustic Surveys

Acoustic surveys are generally carried out on spawning and pre-spawning aggregations of fish. Outside of the spawning season many pelagic species are generally very scattered over a large geographical area and difficult to detect using acoustic methods. A cruise track is first formulated with data from previous surveys, commercial catch data and the help of the fishermen and fishing industry.

Purpose of Survey

The aim of an acoustic survey is to determine the relative abundance of the target species. This information is then used to determine catch rates and management advice for the following year.

How Acoustic Surveys Work

These surveys use sound waves emitted from a "transducer" to estimate the density of plankton and fish shoals. The survey vessel tows the transducer under water, which is linked to an echo sounder in the vessel which records the shoals of fish as "marks" on a screen or paper trace.

'Mark' of herring as seen on acoustic screen. The solid red line is the seafloor.

The species composition of each mark is then identified by taking trawl samples. The density and number of marks are then converted into biomass (weight) of the different species. Acoustic surveys are particularly effective on shoaling species that have a large swim bladder, such as herring and blue whiting.

Marine Institute Acoustic Survey Programme

We carry out acoustic surveys for three main species:

Herring

Blue Whiting

Boarfish

Celtic Sea Herring Acoustic Survey

In the southwest of Ireland and the Celtic Sea (ICES Divisions VIIaS, g & j), herring are an important commercial species to the pelagic and polyvalent fleet. Each year since 1989 FEAS carry out a herring acoustic survey in the Celtic Sea and VIIj, Since 2004 the survey has been carried out in October on-board the RV Celtic Explorer. The geographical confines of the annual 21 day survey have been modified in recent years to include areas to the south of the main winter spawning grounds in an effort to identify the whereabouts of winter spawning fish before the annual inshore spawning migration. As well as studying the target species, each survey also collects oceanographic data as well and provides a platform for students to carry out their own research, and for observers to record seabird and marine mammal activity.

Typical survey track of the Celtic Sea Herring Acoustic Survey.

Blue Whiting Acoustic Survey

Ireland participates in an International Blue Whiting Acoustic Survey (IBWAS), which as well as the RV Celtic Explorer from Ireland, involves vessels from Norway (RV Kings Bay), the Faeroe Islands (RV Magnus Heinason) and the Netherlands (RV Tridens) in spring each year. The total combined area coverage extends from the Faroe Islands in the north (60.30°N) to south of Ireland (52°N), with east -west extension from 6°-17° W. The 2018 survey was the 15th coordinated international blue whiting spawning stock survey since 2004.

Cruise track of all vessels involved in International Blue Whiting survey.

Western European Shelf Pelagic Acoustic Survey (WESPAS)

The WESPAS survey program is the consolidation of two existing survey programs carried out by FEAS. The Malin Shelf herring acoustic survey has been carried out annually since 2008 and reports on the annual abundance of summer feeding aggregations of herring to the west of Scotland and to the north and west of Ireland from 54°N to 58°30’N. The boarfish survey was carried out from 2011 using a chartered fishing vessel and reports on the abundance of spawning aggregations of boarfish from 47°N to 57°N. Since 2016 both surveys have been combined and carried out on-board the RV Celtic Explorer over a 42 day period in June/July providing synoptic coverage of shelf waters from 47°N northwards to 58°30’N.

Typical survey track of the WESPAS Survey.

The International Ecosystem survey in the Nordic Seas

Ireland also takes part in the International Ecosystem survey in the Nordic Seas. This is an acoustic survey for Atlanto-Scandian herring and blue whiting in the Norwegian and Barents seas. It takes place each May on board the Danish research vessel the RV Dana. Ireland sends biologists or acouticians each year. In turn, Danish and German scientists join us on our Blue Whiting Survey each March.